1. Technical Field
Embodiments of the present disclosure relate generally to delay locked loops (DLL), and more specifically to a delay locked loop with offset correction.
2. Related Art
A delay locked loop (DLL) is a closed-loop feedback circuit that adjusts the phase of its output to achieve a desired phase difference between the output and an input signal. The adjustment is typically done based on one or more error signals generated as a comparison result of the phases of the output and the input signal. The input signal and the output are typically clock signals. In addition, a DLL may also provide one or more outputs as phase-delayed versions of the input signal.
With respect to delay locked loops, offset refers to mismatches in the corresponding circuit portions in the DLL, such as, for example, in the phase detector and/or charge pump circuit in the DLL, which lead to a non-zero error being generated even when the output and the input signal are perfectly in-phase. Such offset generally results in the output signal and the input signal not being exactly in phase when the DLL is in the locked condition. Further, due to such offset, the phase-delayed versions of the input signal may not have the desired phase relationship with the input signal. In addition to offset errors, operation of a DLL may be limited by other design aspects such as, for example, the design of the phase detector used in the DLL.